| 摘要 |
<p>PURPOSE:To decrease the number of working steps and improve the yield of material, by punching H-shaped steel in the production stage of said steel. CONSTITUTION:In the stage of rolling rough shape steel with breakdown mills, recesses 7 of a long circuler shape of which the short axis is directed to the web part thereof are formed. Thereafter, the recesses are elongated in the rolling direction by rough universal mill groups. In the rough rolling, the metallic flow in the web part is increased by adjusting the rolling reduction balance between the web part and flange parts. Therefore cracks 71 are produced in the recesses 7 and holes are opened 72. Finally in the finish rolling of H-shaped steel with finishing universal mills or after the finishing rolling, the openings 72 thereof are finished to a true circle 11a of a prescribed diameter.</p> |
